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ECM Power Source Circuit [11/2023 - ]: Procedure

WARNING: This page is about a different car, the 2025 Toyota Corolla Cross and 2024 Toyota Corolla Cross. However, it is still accessible from the selected car via links, so may be relevant.
  1. CHECK TERMINAL VOLTAGE (POWER SOURCE OF EFI-MAIN NO. 1 RELAY) 
    1. Remove the EFI-MAIN NO. 1 relay from the No. 1 engine room relay block assembly.
    2. Measure the voltage according to the value(s) in the table below.

      Standard Voltage

      Tester Connection Condition Specified Condition
      5 (EFI-MAIN NO. 1 relay) - Body ground Always 11 to 14 V
      2 (EFI-MAIN NO. 1 relay) - Body ground Always 11 to 14 V

      Result

      Proceed to
      OK
      NG

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR (AUXILIARY BATTERY - NO. 1 INTEGRATION RELAY) 

    Result: 

    OK 

    See step  2

  2. INSPECT EFI-MAIN NO. 1 RELAY 

    Refer to ON-VEHICLE INSPECTION [09/2021 - ]

    Result

    Proceed to
    OK
    NG

    Result: 

    NG 

    REPLACE NO. 1 INTEGRATION RELAY 

    Result: 

    OK 

    See step  3

  3. CHECK HARNESS AND CONNECTOR (EFI-MAIN NO. 1 RELAY - ECM) 
    1. Disconnect the ECM connector.
    2. Remove the EFI-MAIN NO. 1 relay, D INJ relay, EFI-MAIN NO. 2 relay and EFI-MAIN NO. 3 relay from the No. 1 engine room relay block assembly.

      HINT: 

      Remove the D INJ relay, EFI-MAIN NO. 2 relay and EFI-MAIN NO. 3 relay connected between the checked terminals as the coil inside the relay influences the measurement value.

    3. Measure the resistance according to the value(s) in the table below.

      Standard Resistance

      Tester Connection Condition Specified Condition
      3 (EFI-MAIN NO. 1 relay) - A199-21 (+B) Always Below 1 Ω
      3 (EFI-MAIN NO. 1 relay) - A199-51 (+B2) Always Below 1 Ω
      1 (EFI-MAIN NO. 1 relay) - A199-26 (MREL) Always Below 1 Ω
      3 (EFI-MAIN NO. 1 relay) or A199-21 (+B) - Body ground and other terminals Always 10 kΩ or higher
      3 (EFI-MAIN NO. 1 relay) or A199-51 (+B2) - Body ground and other terminals Always 10 kΩ or higher
      1 (EFI-MAIN NO. 1 relay) or A199-26 (MREL) - Body ground and other terminals Always 10 kΩ or higher

      HINT: 

      If a short is detected in any of the above circuits, there may be a malfunction in the circuit of a connected ECU.

      Result

      Proceed to
      OK
      NG

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR 

    Result: 

    OK 

    See step  4

  4. CHECK HARNESS AND CONNECTOR (ECM - BODY GROUND) 
    1. Disconnect the ECM connector.
    2. Measure the resistance according to the value(s) in the table below.

      Standard Resistance

      Tester Connection Condition Specified Condition
      A199-22 (E1) - Body ground Always Below 1 Ω

      Result

      Proceed to
      OK
      NG

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR 

    Result: 

    OK 

    See step  5

  5. CHECK HARNESS AND CONNECTOR (IGP-MAIN RELAY - BODY GROUND) 
    1. Remove the IGP-MAIN relay from the No. 1 engine room relay block assembly.
    2. Measure the resistance according to the value(s) in the table below.

      Standard Resistance

      Tester Connection Condition Specified Condition
      2 (IGP-MAIN relay) - Body ground Always Below 1 Ω

      Result

      Proceed to
      OK
      NG

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR 

    Result: 

    OK 

    See step  6

  6. CHECK TERMINAL VOLTAGE (IGP TERMINAL VOLTAGE) 
    GTY1181188Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
    *a Front view of wire harness connector
    (to ECM)
    1. Disconnect the ECM connector.
    2. Turn the ignition switch to ON.
    3. Measure the voltage according to the value(s) in the table below.

      Standard Voltage

      Tester Connection Condition Specified Condition
      A199-30 (IGP) - Body ground Ignition switch ON 11 to 14 V

      Result

      Result Proceed to
      OK A
      NG (w/ Smart Key System) B
      NG (w/o Smart Key System) C

    Result: 

    A 

    PROCEED TO NEXT SUSPECTED AREA SHOWN IN PROBLEM SYMPTOMS TABLE. Refer to  PROBLEM SYMPTOMS TABLE [11/2023 - ] 

    Result: 

    C 

    See step  8

    Result: 

    B 

    See step  7

  7. CHECK HARNESS AND CONNECTOR (CERTIFICATION ECU (SMART KEY ECU ASSEMBLY) - IGP-MAIN RELAY) 
    1. Disconnect the certification ECU (smart key ECU assembly) connector.
    2. Remove the IGP-MAIN relay from the No. 1 engine room relay block assembly.
    3. Measure the resistance according to the value(s) in the table below.

      Standard Resistance

      Tester Connection Condition Specified Condition
      I223-24 (IGPD) - 2 (IGP-MAIN relay) Always Below 1 Ω
      I223-24 (IGPD) or 2 (IGP-MAIN relay) - Body ground and other terminals Always 10 kΩ or higher

      Result

      Proceed to
      OK
      NG

    Result: 

    OK 

    GO TO SMART KEY SYSTEM. Refer to  HOW TO PROCEED WITH TROUBLESHOOTING [11/2022 - ] 

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR 

  8. INSPECT IGNITION OR STARTER SWITCH ASSEMBLY 

    Refer to INSPECTION [09/2021 - ]

    Result

    Proceed to
    OK
    NG

    Result: 

    NG 

    REPLACE IGNITION OR STARTER SWITCH ASSEMBLY. Refer to  REMOVAL [09/2021 - ] 

    Result: 

    OK 

    See step  9

  9. CHECK HARNESS AND CONNECTOR (IGNITION OR STARTER SWITCH ASSEMBLY - IGP-MAIN RELAY) 
    1. Disconnect the ignition or starter switch assembly connector.
    2. Remove the IGP-MAIN relay from the No. 1 engine room relay block assembly.
    3. Measure the resistance according to the value(s) in the table below.

      Standard Resistance

      Tester Connection Condition Specified Condition
      I12-8 (IG1) - 2 (IGP-MAIN relay) Always Below 1 Ω
      I12-8 (IG1) or 2 (IGP-MAIN relay) - Body ground and other terminals Always 10 kΩ or higher

      Result

      Proceed to
      OK
      NG

    Result: 

    OK 

    REPAIR OR REPLACE HARNESS OR CONNECTOR (AUXILIARY BATTERY - IGNITION OR STARTER SWITCH ASSEMBLY) 

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR 

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